This surgical device is designed to displace or to penetrate emboli found in the human vasculature. The device has several major components including a proximal (or displacing cage) and a distal filter. Depending upon the chosen procedure, the device is inserted so that the displacing or proximal cage is either towards the venous side of the clot or adjacent the clot. The proximal cage is expanded either to displace the clot away from the arterial wall and allow flow of fluid (e.g., blood and medications such as anti-thrombolytics or other lysing agents) past (or to) the formerly occluded site or to engage the clot for removal using the cage as a collector assembly, expand once past the target emboli, and catch or net the embolism (or a portion of the embolism) for removal from patient's blood vessels. In some situations, the device may be used to move the clot to another position in the vasculature; perhaps for recovery using another device or to canalize the clot for improved blood flow. The distal filter member is always placed distal to the thrombus to catch any portions which may break away.
Other devices to treat vascular emboli are known. The use of inflatable balloons to remove emboli has been practiced for many years. The "Fogarty catheter" has been used, typically in the periphery, to remove clots from arteries found in legs and in arms. These well known devices have been described in some detail in U.S. Pat. No. 3,435,826, to Fogarty and in U.S. Pat. Nos. 4,403,612 and 3,367,101. These patents describe a balloon catheter in which a balloon material is longitudinally stretched when deflated.
Emboli occasionally form around the valves of the heart and then are dislodged and follow the blood flow into the distal regions of the body. They are particularly dangerous if the emboli passes to the brain and causes an embolic stroke. As will be discussed below, many such occlusions lodge in the middle cerebral artery (MCA), although such is not the only site where emboli come to rest. Obviously, when blood flow is inhibited or cut off completely from a portion of the brain, the brain's oxygen supply is limited causing severe health problems.
In procedures for removing emboli using the Fogarty catheter or other similar catheters, it is typical, first, to locate the clot using fluoroscopy. The embolectomy catheter is then inserted and directed to the clot. The distal tip of the balloon catheter is then carefully moved through the center of the clot. Once the balloon has passed through the distal side of the clot, the balloon is inflated. The balloon catheter is then gradually and gently withdrawn. The balloon, in this way, acts to pull the clot ahead of the balloon. The majority of procedures using a Fogarty catheter repeat these steps until the pertinent vessel is cleared of clot material.
Such vaso-occlusions occur in a wide variety of sites within the body. The lodging of thrombus in various sites is often complicated by the presence of atherosclerosis. This disease causes the vessels to become tortuous and narrowed. These anomalies are often considered to be the result of the growth of atherosclerotic plaque. Clots occurring in these diseased vessels are difficult to remove using balloon or Fogarty catheters.
Removal of emboli using balloon catheters is rife with potential problems. One such problem occurs during removal of a clot. The resistance to such removal often causes the balloon portion of the catheter to evert over the tip of the catheter. Should the user need to partially deflate the balloon during such a deflation, the distal tip of the balloon may become distended and angulate. Another difficulty with balloon catheters is the possibility of damage to the intima of arteries. Inflation pressures can create forces significant enough to score such a vessel lining or dislodge plaque lodged on such a wall. In the worst case, the balloon may rupture leaving balloon portions in the bloodstream.
Movement of a balloon in the MCA using only a balloon can displace the clot through more proximal branches into other large vessels such as the internal carotid artery (ICA) and then into other vessels and may pressure the clot into branching vessels.
There are a variety of different devices intended for use in replacing balloon catheters and in using a device other than a balloon catheter in so removing the emboli.
One such device is shown in U.S. Pat. No. 4,030,503 to Clark III. This patent describes a spiral helix affixed to the distal end of a catheter. In particular, the spiral helix is designed to be rotated and pushed forward through the clot. It is said that the helix screws into the clot, and when it is firmly embedded or is past the clot, the catheter is pulled out of the vessel without rotation. The catheter is said to operate like a corkscrew.
A similar catheter is described in U.S. Pat. No. 4,706,671 to Weinrib. This catheter also has a coil section at its distal end. The coil section is said to be stretched initially into a generally linear insertion position for removing inwardly in a vessel. The coil member is then expanded into-the form of a hollow conical scoop to then scoop clot material from the blood vessel. The coil member is stiffened by an internal wire which is then removed. The hollow passageway is then filled with a liquid to stiffen the coils. The coils are said to be of an elastomeric material.
U.S. Pat. No. 4,762,130 to Fogarty et al., describes a helical balloon attached to the distal end of a catheter. The helical or bellowed balloon is maintained in a generally linear condition and passed into a clot. Once the catheter balloon within the clot is inflated, the balloon and adjoining clot are removed together.
Another similar device used more to grip and shear atherosclerotic deposits rather than to remove thrombi is described in U.S. Pat. No. 4,890,611 to Monfort et al. This device incorporates a pair of helical wires placed on the distal end of a wire. The flexible wire is pulled against a flexible catheter and the two helically configured loops expand to form a shearing apparatus. The totality of the apparatus is then twisted by means of a handle so that the pair of helically wound loops cuts through and is said to retain sections of plaque for removal from the vessel.
Another thrombus extraction system is shown in U.S. Pat. No. 5,011,488, to Ginsberg. In using this device, an inflatable balloon having a proximal conic shape is deflated and passed through a thrombus. It is then expanded and retracted so that the proximal passage pulls the thrombus into contact with an aspirator. The aspirator then removes the clot or thrombotic material from the vessel.
An alternative configuration of the expandable member is also described in the Ginsberg patent mentioned just above. In this variation, a wire coil is attached to an extension wire which may be moved between an extended position and a retracted position. The retracted or expanded configuration is illustrated to have a conical shape. The cone is shown to be one which has a smaller end proximally.
U.S. Pat. No. 5,112,347, to Taheri, shows an inflatable balloon type embolectomy catheter. The balloon has a number of fingers arranged in a leaf spring arrangement inside the balloon. The balloon is hydraulically inflated and forms a cone after inflation. The deflated device is shown in FIGS. 11 through 14 to be passed distally past an embolism before inflation. After inflation, the large end of the balloon collects the embolism as it is pulled past the appropriate site in the vessel.
U.S. Pat. No. 5,192,286, to Phan, shows a retrieval catheter for removing materials from various body lumen. The retrieval catheter is shown to have a slack net which may be collapsed for passage into a lumen past the material to be collected. The net is unfolded and materials such as uretral stones are removed.
U.S. Pat. No. 5,411,509 to Hilal, shows an embolectomy catheter having an elastomeric foam tip attached distally. The foam tip has an actuator means suitable for forming the foam section both longitudinally and radially in response to activation of the actuation means. In practice, the catheter tip is pressed past an embolism, inflated, and retracted with the clot being pushed proximally retraction occurs.
U.S. Pat. No. 5,490,859, to Mische et al., shows an intravascular occlusion material removal device having an expandable material removal element made up of a number of wires passing between the two ends of such element, a catheter shaft, a drive shaft for spinning the material movement element within the blood vessel, and a collection portion placed on the material removal element for collecting any occlusion material removed by the expandable material removal element. The drive shaft may be operated by a motor connected to the proximal end of the drive shaft.
None of these devices show the device described below.